One aspect of the present invention relates to a system for depositingxe2x80x94e.g. xe2x80x9cwritingxe2x80x9dxe2x80x94materials on a target while simultaneously monitoringxe2x80x94e.g. xe2x80x9creadingxe2x80x9dxe2x80x94the deposition process.
It is well known that passing beams of unfocussed charged particles through a magnetic field causes the constituent particles to separate according to particle charge-to-mass ratio and/or velocity. This is the basic principle of mass spectroscopy. A byproduct of the passage of such a beam through a magnetic field is the introduction of uncorrectable resolution-limiting aberrations to any subsequent images in the beam.
Rempfer and Mauck in a paper entitled Correction of Chromatic Aberration with an Electron Mirror, Optik Vol 92, No 1, (1992), disclosed that an image could be passed through a cylindrical magnetic turning field (CMTF) without limiting resolution if a real image were formed at the center of the magnetic field. In other words, the beam incident on the CMTF is focused at its center and thus may be refocused by a lens back to a single image without loss of resolution. Such a geometry is not useful for mass spectrometry because subsequent images in the beam are not easily separated by ion mass as they are in a system where the ions pass through a magnetic field substantially collimated. In other words, a mass spectrometry system uses an unfocused beam incident on the magnetic field. Then the beam normally passes through a lens and is separated into different ion masses.
FEI Company sells an XL800 Full Wafer Scanning Microscope which uses an ion beam for erodingxe2x80x94xe2x80x9cmachiningxe2x80x9d xe2x80x94a surface, and an electron beam for probing and monitoring the progress of erosion. The two beam-forming structures are separate but physically proximate one another.
Chromatic And Spherical Aberration Correction
Just as light beams passed through optical lenses will experience resolution-limiting spherical and chromatic aberrations, so beams of charged particles passed through electrostatic and electromagnetic lenses also include these aberrations, due primarily to two factors:
1. spherical aberrations are due to the failure of a lens to focus particles at different lateral distances from the axis thereof to the same point longitudinally on the axis, i.e., for a converging lens and particles incident upon the lens parallel to the axis, particles farther from the axis are focused nearer the lens than particles closer to the axis; and
2. chromatic aberration are due to the failure of a lens to focus particles of different energies to the same point on the axis. Chromatic and spherical aberration may also be introduced into electron optical systems from the sources of the beams. Where energy aberration becomes significant, it can be reduced by passing the beam through an energy filter at the expense of reduced beam current.
Henneberg, U.S. Pat. No. 2,161,466, teaches that the aberrations of electrostatic mirrors have the opposite sign from those of electrostatic and electromagnetic lenses, and that such mirrors could in principle be used to correct spherical and chromatic aberrations of lens systems and beam sources. Rempfer and Mauck, Optik, 1992 discovered that incident and reflected beams of charged particles could be separated if the single homogenous beam is focused upon and passed through the geometric center of a substantially cylindrically symmetrical magnetic field, where the field is located at an image plane of a particle beam lens. In that system, two lenses were used to relay an image between each deflecting field, and small magnetic beam deflection angles were necessary in order to prevent magnetic field distortion effects. Unfortunately, such a system is complicated and the deflection angles are small. Further, small deflection angles cause distortion in the beam exiting the magnet.
Hereinafter, the term xe2x80x9cincident beamxe2x80x9d refers to a beam of charged particles which is directed toward an element which modifies it in some way.
Hereinafter, the term xe2x80x9creflected beamxe2x80x9d or xe2x80x9cexiting beamxe2x80x9d refers to a beam of charged particles which has been modified in some way by interaction with some element.
Leboutet et al., U.S. Pat. No., 3,660,658, disclose a mass separator using a magnetic deflector system which deflects a charged particle beam at an angle of 90 degrees to its initial axis, and which also includes a magnetic deflector which deflects the beam at an angle of 127 degrees. The particle beam of Leboutet et al. passes through the turning magnetic field unfocussed. The Leboutet et al. device relies on the unfocussed nature of the beam to perform the mass separation.
Rose et al., U.S. Pat. No., 4,760,261, disclose an electron energy filter which operates at a preferred angle of 115 degrees. The geometry of Rose et al. incorporates a triangular-shaped magnet. Like Leboutet et al., Rose et al. depend upon separating all but those particles within a narrow selected energy range from a beam of particles having a wide spectrum of energies. Such a device is effective only when using unfocused beams.
Crewe, U.S. Pat. No., 5,336,891, discloses an aberration-free lens system which includes both magnetic and electrostatic components to obtain aberration-free imaging. All examples disclosed by Crewe (FIGS. 3a-3i) show deflections only of 45 degrees, 90 degrees, and 180 degrees.
Rose et al., U.S. Pat. No. 5,449,914, disclose an energy filter in which the beam is deflected four time at angles of 135 degrees. Rose et al. relies on an unfocused beam to perform its functionality.
Wada, U.S. Pat. No. 5,254,417, discloses a reflection mask for producing reflected electrons from the surface of a substrate in a desired pattern. An electron beam is deflected by an electromagnetic field into an electrostatic mirror, from which it is reflected back into the field and deflected to continue in its former direction. Wada does not focus its incident or its reflected particle beams at the geometric center of the respective magnetic deflecting fields.
Rose et al., U.S. Pat. No. 5,319,207, disclose an electron beam passing through magnetic deflection fields B1/B2, deflected 90 degrees into a mirror, reflected back through the magnetic deflector, and deflected 90 degrees onto the object to be scanned. The magnetic deflector taught by Rose et al. is a complex device formed by a pair of circular magnetic poles having sufficient separation therebetween to allow one or more beams of charged particles to pass therethrough. Rose et al. focus their incident beam on the hypothetical diagonal symmetry plane 3g of deflector 3, and their reflected beam on the hypothetical diagonal symmetry plane 3h . 
Magnetic Turning Field
Rose et al., U.S. Pat. No. 5,319,207, further disclose an electron beam passing through magnetic deflection fields B1/B2, deflected 90 degrees into an electrostatic mirror, reflected back through a square magnetic deflector, and deflected 90 degrees onto the object to be scanned. Rose et al. focus their incident and reflected particle beams on hypothetical diagonal symmetry planes. Further, the deflector of Rose et al. is square, and has two magnetic fields which must be adjusted and balanced for strength.
What is desired, is a system for depositingxe2x80x94e.g. xe2x80x9cwritingxe2x80x9dxe2x80x94materials on a target while simultaneously monitoringxe2x80x94e.g. xe2x80x9creadingxe2x80x9dxe2x80x94the deposition process.
The present inventions, in several aspects, overcome the aforementioned drawbacks of the prior art by providing a system for joining at least two beams of charged particles that includes directing a first beam along a first axis into a magnetic field. A second beam is directed along a second axis into the magnetic field.
The first and second beams are turned, by interaction between the field and the first and second beams, into a third beam directed along a third axis.
In another aspect of the present invention a system separates at least two beams of charged particles by directing a first beam along a first axis into a magnetic field where the first beam includes mixed charged particles. The first beam is directed at the magnetic field. The mixed charged particles are separated into at least a second beam and a third beam, by interaction between the magnetic field and the first beam.
In another aspect of the present invention a system turns at least two beams of charged particles by directing a first beam along a first axis into a magnetic field where the first beam exits the magnetic field along a second axis. A second beam is directed along a third axis into the magnetic field where the second beam exists the magnetic field along a fourth axis. The third axis is at least one of colinear and coaxial with the second axis and the second beam along the third axis has a different direction of travel than the first beam along the second axis.
In another aspect of the present invention a system focuses at least two beams by providing a first beam and a second beam that are coaxial with one another where the charge of the first beam is opposite from the charge of the second beam. The first beam and the second beam are directed through a lens such that the first beam and the second beam are focused at the same plane.
In another aspect of the present invention aberrations are reduced in a beam of charged particles by directing the beam along a first axis to a magnetic field where the beam leaves the magnetic field along a second axis that is not colinear with the first axis. The second axis is directed toward a mirror. The beam is reflected from the mirror along a third axis. The beam is reflected from the mirror along a third axis. The beam is directed along the third axis to the magnetic field where the beam leaves the magnetic field along a fourth axis that is not colinear with the first axis.
In another aspect of the present invention a system for depositing particles on a target and monitoring the depositing includes providing a first beam of ions, a second beam of electrons, and combining the first beam and the second beam into a coaxial third beam by interaction between the field and the first and second beams. The ions are deposited from the third beam on the target. The deposition is monitored with the electrons of the third beam.
In another aspect of the present invention a system for depositing at least one ionized atom on a target and moving the at least one atom into a desired position include at least one ionized atom from a first source that is directed to a magnetic field along a first axis, and toward the target along a second axis different from the first axis by interaction of the at least one ionized atom and the magnetic field. At least one electron from a second source is directed to the magnetic field along a third axis, and toward the target along a fourth axis by interaction of the at least one electron and the magnetic field. The at least one ionized atom is deposited on the target. The at least one electron is directed in such a manner as to move the deposited at least one ionized atom on the target to a desired position.